Centerboad Pin

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Editors
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Centerboad Pin

Post by Editors »

There have been a variety of approaches to installing the SCAMP centerboard pin. This thread will be used to detail some of these methods. Thank you to everyone who contributes to this and other aspects of SCAMP development. —Josh
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Re: Centerboad Pin

Post by Editors »

ImageCenterboard Pinadaptation a la Eric Leif

His SCAMP #387 is Birdy and is in Lawrence Kansas

The head of the centerboard pin is located in the water ballast tank, a change from the SCAMP Builder’s Manual.

How to install the centerboard pin...
I like the approach Howard Rice described with access in the water ballast tank, so tried something like that...

I used the same 1/2" bronze drain plug used for the water ballast tank drain. I drilled and tapped the end of the pin, screwed a bolt in the end (epoxied it too for good measure), and drilled a hole in the drain plug to accommodate the bolt end when the plug is tightened down.

I can pinch the bolt that sticks out with my fingers and pull the pin out. But the first couple of times it got really stuck in there. Threading a wing nut on the end of the bolt and tightening against the drain flange works like an extraction tool, and the pin pops right out, even if it's binding up. there is about an 1/8" of side-to-side pin-play when the drain plug is tightened down. A stainless washer is glued to the wood cap at the other end to keep the pin from wearing on the wood.

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Re: Centerboad Pin

Post by Editors »

Howard Rice’s Centerboard Pin

Compiled from Howard Rice’s notes and photographed by Simeon Baldwin.

The head of the centerboard pin is located in the water ballast tank, a change from the SCAMP Builder’s Manual.

On the outboard side of the centerboard case is a 9mm thick 2.5"x2.5" plywood plate glued and screwed to the case side. This is a back stop or closed end for the pin.

On the inside of the centerboard case I have installed a 2.5"x2.5" 9mm plywood plate with a 1.5" brass plumbing fixture that has a screw in cap. The inside diameter opening at 1" (I think?). Point being it has to be large enough to house the pin, with room enough to get a pair of needle nose vise grips in to pull the pin should the lanyard fail for some reason.

I just made the hole large enough in the 9mm mounting plate to fit the outside threads, sort of jammed it in buried in glue, nice tight fit and with glue all through the outside threads so its leak proof. I cut the length (depth) of the brass fitting just a little with a hacksaw to make it flush with the 9mm plate............it almost fit just right and with the trim off it fits nicely.

I drilled into the end of the centerboard pin and inserted (epoxied in) a small stainless screw. On the screw and captured by the screw head I have epoxied a small (2" long) lanyard. Simple ss screw. I tapped the end of the pin and put in the screw. I figured the lanyard might want to be replaced over time so left the screw a little proud, easy to nip off the lanyard and tie on a new one.

Once the board is in and the pin pushed all the way into place I curl up the lanyard and push it into the opening in the plumbing fitting, place the cap on, tighten it with a wrench thus creating a 100% watertight centerboard pin set up. The cap prevents the pin from backing out.

The screw in cap is hollow, nice and deep hollow, but not really needed (full depth). It does not impact the cbd pin and end screw with lanyard.

The whole interior of the water ballast tank and the assembled set up was coated in graphite in epoxy.

If I need to remove the board I open the 6" Beckson screw in port in the floor (ballast tank fill port), reach in with a small wrench, back off the cap, grab the lanyard and pull the pin.
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Re: Centerboad Pin

Post by GregWads »

I plan to implement Eric Leif's design on Scamp #337. But I do not have the metal working skills or capabilities of Eric. Before the current madness struck, I talked to a local, one off, prototyping metal shop about making the pin. Rather than drill and tap, they told me they would prefer to machine the pin from a 316 Stainless bar stock and gave me a rough estimate of around $80 a pin. Also, if I purchased more than 5 the price per unit would be less. I told them I would get back to them when I knew the exact dimensions, but realistically the only important dimension would be the length of the treads. If you just left the other end long, it could always be cut back to the appropriate length.
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Re: Centerboad Pin

Post by dndrich »

I did something similar to what Howard described. I have 1/2 inch internal diameter bronze bushings bought at McMaster-Carr glued into the walls of the centerboard trunk. On the locker side I have 2 pieces of 9 mm ply glued as a cap, one of which has a 3/4 inch hole in it to give space for the pin to stick out a bit. The pin is a 1/2 inch diameter 316 steel clevis pin of the right length, again from McMaster-Carr. Now, on the tank side I glued another 9mm piece of ply with a 1 inch hole, made to receive a brass threaded pipe end, cut to size, perhaps an inch long or so. The brass pipe is glued in, and can be capped with the brass cap as seen. Easily purchased at any hardwares store. Now, I had a friend drill and tap the end of the clevis pin so that I could put in a #8 screw so I can easily pull the pin, and made it the length that it would just fit inside the closed cap. The clevis pin is flanged, so that it won't hit the cap in the locker side, but is trapped with minimal play in the tank side. The pin is very easy to pull. Now, you could use the same clevis pin, and just tie a lanyard around the flange to make it easier.

One interesting problem is that it is really hard to get everything completely square in x,y, z dimension while building, so that when I tried to put the pin in the board for a test in the trunk, it would just not pass even though the pin easily passes to the other side without the board. I think my hole in the trunk is perhaps 1-2 mm higher inboard than outboard, and that gives enough tilt in the board to prevent it from going in. It was very frustrating. So, I drilled out the 1/2 inch bushings in the board, and replaced them with 9/16 internal diameter bushings, and that small amount of play was enough to allow the pin to pass through the board to the other side well.

I would recommend doing that. The pin is not really where the board gives the boat drive. It simply keeps the board from falling out of the boat. The drive comes from the flat sides of the board contacting the trunk. So, make it easy on yourself and slightly oversize the board bushings. Otherwise you have to build the board and trunk at the same time, and before gluing in make sure all is perfectly square somehow, or just get lucky.

Clevis pin with screw in end
Image

Cap before paint in locker side under seat
Image


Image
Image
Daniel
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Re: Centerboad Pin

Post by simeoniii »

SCAMP #501, a kit build by Israel on Bainbridge Island Washinton, has yet another centerboard pin design.

He has gone with insertion of the pin from within the water ballast tank, a method that now seems to be preferred. He used a 1/8" EPDM closed-cell rubber gasket on the WB tank side.
He is using an 8" port in the sole above to allow easier access.
CB Pin-1-compressed 2.JPG
CB Pin-2-compressed 2.JPG
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Re: Centerboad Pin

Post by jfhbc »

I'm gathering materials to start a build (#584) and been reading through the various threads.

I have in mind a slightly simpler method for the CB pin that builds on everything discussed on this thread. Wanted to bring it up here for discussion.

My idea is to use two threaded 1.5" pipe nipples (size 1/2 pipe, i.d. 0.622", sku 9580K23 at McMaster... these guys: https://www.mcmaster.com/pipe/threading ... -size~1-2/) through the boards as both bushings and cap receptors. The centerboard would still use the 0.5" bronze bushings. The i.d. on each pipe is slightly wider (1/8") that the o.d. of the pin, allowing for the play that Daniel mentions is important to allow everything to line up. The play would be between the side pipes and the pin, not the CB bushings.

The pin itself would use Daniel's idea of a bolt at the end of the pin (though these come ready made! McMaster calls them "pull out dowel pins": https://www.mcmaster.com/pins/pull-out- ... /length~3/

My improvement would be the addition of a tightening nut along the bolt shaft to secure the bolt into the pin and thereby adjust the total pin length - one could then tailor the pressure with which the pin is held between the two end caps of the pipes: no lateral play.

Note that the pin in the drawing is drawn below the two pipe fittings, but really would fit in them. I just drew it below for clarity with the bolt and nut.

Any input or obvious gotchas from those who have gone before me?
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Re: Centerboad Pin

Post by dndrich »

That should be great!
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Re: Centerboad Pin

Post by jfhbc »

Following up on this, after a summer's field use: the design works great! Super snug, completely waterproof (never had a leak in the locker) and eminently field-maintainable, since the entire pin assembly can be removed without tools. No drawbacks that I could find.

The build process is essentially 1. overdrill hole where pin will be, 2. fill overdrilled hole with epoxy, 3. re-drill appropriate diameter hole to accept the threads on the short pipe lengths, 4. screw in pipe nipples and glue in place. The pin can be used to line up the two pipe ends so they're true and the pin will slide in smoothly once it's all put together.

Some visuals:

The overdrilled, filled, and re-drilled hole, from the inboard side (e.g. towards ballast tank):
Image

Ditto, from the centerboard side:
Image

With the nipple inserted (seeing the outer starboard side, the part that sticks out into the starboard locker between B4 and B5):
Image

Same view, with the cap on. This is the part that lives inside the starboard locker:
Image

View of the pin and spacing bolt protruding from the setup. This is the part that protrudes into the ballast tank. The bolt can be screwed to adjust the length of the pin+bolt inside the caps for a snug lateral fit:
Image

View of the pin in place in the centerboard case:
Image

In the end I went with "Thick Walled" threaded nipples not because of the thick wall, but because the inner diameter matched the pin more closely, thereby providing a snugger fit (0.546" ID vs 0.622" on the original idea). This also required a more accurate placement and less margin for alignment errors, so you might prefer to go with the nipples described in the previous post (0.622" ID) if that's your preference.

If anyone would like to build the pin assembly this way, here are the part numbers from McMaster-Carr:

Thick Walled Threaded Brass Nipple (x2) 9149K14
Stainless Pull-Out Dowel Pin, 0.5" x 4" (x1) 97175A899
High-Pressure Brass Pipe Fitting (x2) 50785K163
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